Despite their widespread use over the past fifty years, intelligence tests remain highly empirical and relatively atheoretical devices. This situation is at least partially due to the greater emphasis traditionally placed on the predictive validity of intelligence tests as opposed to the elaboration of intelligence as a theoretical construct. One of the consequences of the strong influence of applied psychology on human ability research is that a schism has developed between the psychometrician and the experimental psychologist. Thus, although the study of human cognition is currently more intense than at any previous time, most current theories of cognition do not deal in any detail with individual differences. The purpose of the proposed research is to begin to lay the groundwork for a rapprochement between psychometrics and the experimental study of cognition. A series of experiments designed to reveal the relationships between the traditionally measured traits of verbal, motor, and quantitative ability on the one hand, and the parameters of typical information-processing models of cognition on the the other are proposed. By examining a variety of intellectual tasks, it should be possible to find those parameters that are most crucial in determining different types of intellectual performance. Tests may then be devised to directly measure these parameters. Collectively, these tests would constitute a theoretically based measure of intelligence. Moreover, such a measure would be diagnostic rather than merely descriptive, since it could more precisely define what aspects of intelligence are potentially modifiable and how such modifications may be obtained.